High temperature combustion is often employed in many industrial processes such as in glassmelting. Corrosion and fouling of burner nozzles are common problems in high temperature industrial processes. Water cooling of metallic nozzles is often used to prevent high temperature corrosion or melting. Although water cooling is effective in a relatively clean furnace atmosphere, it adds to the complexity of the combustion system and also could escalate the corrosion and fouling problem when the furnace atmosphere contains condensible vapors. Ceramic nozzles have been proposed for use with high temperature combustion as a way for avoiding water cooling. However, presently available ceramic nozzles tend to develop cracks due to thermal and other stresses and are not considered dependable for many industrial applications. The problem of designing a non-water cooled burner is particularly severe where the burner employs oxygen or oxygen-enriched air rather than air as the oxidant because of the high flame temperature generated.
High temperature combustion may be carried out by injecting fuel at a high velocity into a furnace zone as this enables the major part of the combustion reaction to be well away from the nozzle or fuel injection point. Furthermore the fuel injection may occur in a cavity communicating with the furnace for further protection of the nozzle. Other heat protection steps include employing a flame detached from the burner nozzle and operating within a cavity having an expanded flow area. However, high velocity fuel injection may cause the generation of an excessively long flame length.
Accordingly, it is an object of this invention to provide an improved combustion method which may effectively employ high velocity fuel injection for carrying out high temperature combustion without the need for water cooling of the fuel injection nozzle and without generating an excessively long flame.